The present invention pertains to right angle or elbow attachments for power driven tools, and more particularly pertains to elbow attachments for mounting to power tools to drive an output shaft perpendicular to the drive shaft of the power tool.
Several elbow attachments for use with power tools are currently available in the marketplace; however, each of the presently available elbow attachments suffers a significant shortcoming. Currently available elbow attachments are of two general types.
One type of commonly employed elbow attachment utilizes a pair of bevel gears to transfer the torque from the drive shaft of the power tool to the transverse shaft of the elbow attachment, which transverse shaft is supported by the elbow attachment housing perpendicular to the power tool drive shaft. That is, a first bevel gear is mounted to the drive shaft of the power tool, and a second bevel gear is mounted on the transverse shaft of the elbow attachment. The first and second bevel gears are disposed such that when the elbow attachment is mounted to the power tool, the first and second bevel gears mesh to effect transfer of the torque from the power tool drive shaft to the transverse shaft of the elbow attachment. A particular shortcoming of this type of elbow attachment is that it is necessary for the two bevel gears to be accurately positioned with respect to one another for the gears to properly mesh. Hence, this arrangement does not allow for any significant variability in the positions of the two bevel gears, and therefore it does not allow for any variability in the precise position at which the elbow attachment is mounted on the power tool. Since it is difficult to provide such high precision in the mounting of the elbow attachment to the power tool housing without increased complexity of design and/or cost, elbow attachments which utilize a pair of bevel gears are subject to improper meshing of the bevel gears and accelerated wear, as well as increased noise.
In another type of commonly employed elbow attachment, the housing of the elbow attachment supports both a longitudinal shaft and a transverse shaft, with the shafts supporting respective gears which mesh with one another to transfer the torque from the longitudinal shaft to the transverse shaft. The longitudinal shaft is engageable with the drive shaft of the housing and is disposed for rotation together with the drive shaft about the drive shaft axis. The transverse shaft extends perpendicular to the longitudinal shaft. The longitudinal and transverse shafts are maintained in their respective positions within close tolerance, such as by their support on respective bearings, and therefore the gears maintain good meshing. A particular shortcoming of this type of elbow attachment is its requirement of the longitudinal shaft and its associated bearings, which add significantly to the cost and size of the device.
Accordingly, there is a need for an elbow attachment which allows for some variability in its engagement with a power tool housing while still maintaining good meshing of the gears which transfer the torque to the transverse shaft, and which does not require a second shaft and associated bearings in addition to the transverse shaft to allow for a lower cost product.
In accordance with the present invention, an elbow attachment is provided for use with power tools having a housing which supports a drive shaft which is rotary about its longitudinal axis and which protrudes externally of the power tool housing at a driving end of the housing.
A pinion gear is detachably mountable directly on the drive shaft of the power tool at a location externally of the power tool housing and at a predetermined distance from the driving end of the housing, with the pinion gear having gear teeth with faces of predetermined face width which extend substantially parallel with the longitudinal axis of the power tool drive shaft. An elbow member is provided, comprising an elbow member housing having a power tool engaging end which is engageable with the power tool housing adjacent its driving end, with a transverse shaft having a longitudinal axis and supported by the elbow member housing to be substantially perpendicular to the longitudinal axis of the drive shaft of the power tool upon engagement of the elbow member housing with the power tool housing, with the transverse shaft having a tool engaging end disposed externally of the housing for engaging a tool, and with a face gear having gear teeth which extend substantially parallel with respect to the longitudinal axis of the transverse shaft, with the face gear being mounted on the transverse shaft at a predetermined position at which the teeth of the face gear are engageable with the teeth of the pinion gear when the elbow member housing is engaged with the power tool housing.